Add EUnit plugin
Fix error in EUNIT_ERLC_OPTS
Sort build.config in alphabetical order
Set 'logs' as the default report dir
Add help-eunit target
Add support for specifying EUnit dir
Replace erl-join by str-join
Improve support for external tests dir
Use erlang:halt/0 instead of init:stop/0
Merge branch 'refs/heads/pulls/eunit' into custom